In recent years, radio frequency identification (RFID) tags such as contactless IC smart cards are in use. The RFID tags receive power supply and information from external devices such as reader/writers and send information to the external devices in a contactless manner via radio waves.
An RFID tag includes an integrated circuit (IC) chip and an antenna in an embedded form inside a card shape. The RFID tag can read information from or write information into a reader/writer in a contactless manner via radio waves.
As an already existing application, the RFID tags are used in, for example, a physical distribution management system (using linen tags) for managing articles of clothing such as uniforms. It is necessary for such linen tags to preserve the feel of clothes when put on and to have a certain level of strength.
More particularly, since an RFID tag that is attached to an article of clothing gets washed without being removed from that article of clothing, it is necessary for the RFID tag to be able to withstand the bending stress that acts thereon during washing.
In order to maintain the strength and durability of an RFID tag, the exterior body of an inlet disposed therein needs to have a rigid structure. However, on the negative side, the rigid structure of the inlet affects the wear comfort of the clothing.
In a typical RFID tag used as a linen tag, an inlet disposed inside the RFID tag is enclosed with urethane or the like. However, if such an RFID tag happens to bend during washing, then the bending stress acts directly on the inlet thereby causing disconnection of an antenna pattern mounted thereon.
In regard to the problem regarding the strength of RFID tags, Japanese Unexamined Utility Model Application Publication No. 2000-733 discloses a technology in which an antenna substrate in an RFID tag is protected with a pair of a upper film and a lower film that are made of fluorine contained resin.
Moreover, Japanese Laid-open Patent Publication No. 11-102424 discloses a technology in which a gelled resin is filled in the inside part of an RFID tag and the inside part is covered with an exterior cladding so that the RFID tag is prevented from stress deformation.
Furthermore, Japanese Laid-open Patent Publication No. 2007-272748 discloses a technology of strengthening an IC chip in an RFID tag by covering the IC chip with a hardening adhesive film.
Moreover, Japanese Laid-open Patent Publication No. 2008-97426 discloses a technology in which a foam polystyrene plate is sandwiched between the inlet in an RFID tag and a metal plate having a slit formed thereon so that the inlet is protected from unnecessary external force.
However, following problems occur in the RFID tags manufactured using the conventional technology. Consider the case of an RFID tag manufactured using the technology disclosed in Japanese Unexamined Utility Model Application Publication No. 2000-000733. In that case, although the antenna substrate in the RFID tag is protected with a pair of an upper film and a lower film of fluorine contained resin; it is not possible for the fluorine contained resin to prevent the external force from propagating to the antenna substrate. That makes the antenna substrate vulnerable to damage.
In the case of Japanese Laid-open Patent Publication No. 11-102424, although the gelled resin filled in the inside part of an RFID tag enables preventing the RFID tag from stress deformation; it is not possible to prevent deformation of the antenna substrate.
In the case of Japanese Laid-open Patent Publication No. 2007-272748, although an IC chip is strengthened by covering it with a hardening adhesive film; it is not possible to protect the antenna substrate inside the corresponding RFID tag.
In the case of Japanese Laid-open Patent Publication No. 2008-97426, although the metal plate having a slit formed thereon gets twisted so that the inlet is protected from unnecessary external force; the same reinforcement does not necessarily work against bending.